APPLICANT'S ABSTRACT: This is an application for a Scientist Development Award. The long term objectives of this proposal are to establish the possible role of ALDH5 in acetaldehyde metabolism. This will involve purification and physical characterization of the ALDH5 protein. These objectives will lead to studies to ascertain the mechanism of liver- specific ALDH5 gene expression. The hypothesis that ALDH5 plays a significant role in acetaldehyde metabolism stems from preliminary experiments which indicate that ALDH5 has a low Km (-20 uM) for short chain aldehydes. In addition there is a high degree of homology between ALDH5 and ALDH2, the major acetaldehyde metabolizing enzyme. Characterization of ALDH5 will involve purification of the recombinant bacterially expressed protein, determination of its molecular weight, determination of various kinetic parameters and substrate preference, determination of subcellular localization, and an examination of the promoter elements responsible for liver-specific gene expression. The immediate objectives of this application will continue work which involves ALDH2 gene expression, which centers around the purification of a novel liver-specific transcription factor. I have had a long standing interest in alcohol research which began with my thesis work studying the transcriptional regulation of the human Class I alcohol dehydrogenase genes. A career development award would allow me to develop expertise in protein biochemistry and establish an independent alcohol-related research program. Studying the structure and function of ALDH5 as well as characterization of a novel transcription factor involved in ALDH2 gene expression would be a logical direction for me to take in developing into an independent investigator.